django rest framework not updating but adding new object serializers class based view code example

Example 1: User serializer in django rest framework

from rest_framework import serializers

class PostSerializer(serializers.ModelSerializer):
    user = serializers.PrimaryKeyRelatedField(read_only=True, default=serializers.CurrentUserDefault())
    class Meta:
        model = Post

Example 2: User serializer in django rest framework

class Event(models.Model):
    user = models.ForeignKey(to=settings.AUTH_USER_MODEL, on_delete=models.CASCADE)
    date = models.DateTimeField(default=timezone.now)
    place = models.CharField(max_length=255)